1. Field of the Invention:
This invention relates to a film feeding device for a camera.
2. Description of the Prior Art:
In a camera which is used by loading it with a film having perforation providing along the edges thereof such as a 35 mm film and which is arranged to accomplish film feeding to a set length and film rewinding, after photographing, by means of a sprocket which is provided inside the camera, the sprocket which is disposed in the path of the film is allowed to rotate only in response to the operation of a film wind-up lever when the set-length film feeding operation is made, the sprocket then rotating to follow the forward movement of the film to a film take-up spool. For film rewinding, the sprocket is allowed to freely rotate to follow the film movement back to the rewinding side. Therefore, there is provided a driving force transmitting mechanism between the film wind-up lever and the sprocket for the purpose of transmitting the action of the lever to the sprocket. The driving force transmitting mechanism is arranged to rotate the sprocket only to an extent corresponding to the operating extent of the film wind-up lever. Accordingly, the mechanism is readily operable when operated by the film wind-up lever. However, it cannot be readily operated from the sprocket side because of a large load of the transmission arragement thereof. For rewinding film, the film is rewound by means of a film rewinding lever back to a film feeding spool. However, there is provided no cooperative arrangement between the film rewinding lever and the force transmitting mechanism. For rewinding the film by operating the film rewinding lever, therefore, the force transmitting mechanism imposes a load on the sprocket to hinder the smooth rotation of the sprocket. Such hindrance in turn hinders the sprocket from coming into engagement with the perforation of the film and the film cannot be smoothly rewound under such a condition. To solve this problem, in the film feeding device employed in the conventional cameras, there is provided a clutch mechanism between a driving force transmitting mechanism and a sprocket to operate the clutch mechanism in such a way as to disengage the sprocket from the force transmitting mechanism for rewinding the film to ensure free rotation of the sprocket. The conventional clutch mechanism employed in the film feeding device of the conventional camera comprises a center shaft member which is slidable inside a film feeding sprocket and which is provided with a protrudent pin arranged to engage with a slot provided in the sprocket; and a protrudent clutch pin which engages with and disengages from a clutch groove provided in a drive device which rotates in response to a film winding operation. The pin which is provided in combination with the slot of the sprocket allows the center shaft to move alone in the direction of its axis and then causes the sprocket to rotate together with the center shaft when the shaft rotates. On the other hand, the protrudent clutch pin comes to engage with the clutch groove when the center shaft moves to one side within the restriction defined by the protrudent pin and the slot of the sprocket and thus transmits the force of the drive device to the sprocket through the center shaft and the protrudent pin. When the center shaft moves to the other side, the clutch pin, comes to disengage from the clutch groove to release the sprocket from engagement with the drive device to permit free rotation thereof. Thus, in the film feeding device of the conventional camera of this type, the rotation of the drive device is transmitted to the sprocket through the clutch groove, protrudent clutch pin, protrudent pin and the slot. Therefore, when the protrudent clutch pin engages with the clutch groove and the protrudent pin with the slot, if there are any gaps or clearances between these engaging parts, there arises a play which results from the sum of these gaps. Since these engaging parts are very small in diameter, such a play is enlarged at the drive device and becomes a great value there. Under such a condition, even if the sprocket is accurately turned by a film winding operation to a degree of angle exactly corresponding to one frame of the film, the resilience of the film resulting from its wound-up state causes the sprocket to turn backward as much as the degree of the play after the sprocket is stopped. The backward rotation then causes uneven spacing between one picture and another.